Running a fridge as a chiller?

[pomme]

Running a fridge as a chiller?

Ive been thinking of the summer months and the heat on the tank.

just speaking out loud here guys but i have just had a thought, how about having a air pump running in a fridge and then pumping the air from the fridge into the sump where it would cool the water. but be controller by a probe and monitor in the water?

i know it sounds stupid but if it works a tiny bit ans stops the tank water changing to much over the few hot days in the summer then brilliant

Andrew

[Phishnoob]

The only bad thing about air to water conduction is that it is 100 times less effective than water to water. Think about how much faster a can of beer cools down in a cooler with ice water vs. sticking it in the freezer. Plastic tubing has a horrible heat transfer coefficient as well though but my beer fridge chiller helps a lot. I reduced the flow though it and it returns through the UV which I wanted slower flow for as well.

There is a tub of cold water in the fridge and the tubing is all coiled in there so it makes about six loops.

I was running at 82 degrees but this got it down to 80 which was enough for me.

I will post a picture up on the forum when I first installed this. It was just some odd PVC bits and a crappy Rio pump and tubing.

MH's go in this month so it looks like an upgrade in the water bath to a titanium coil is the project for the weekend.

Phishnoob

[Geoff]

what Phishnoob said!!

something that would be better, but more difficult, is to use a room A/C unit. i will be doing one of these over the weekend, i hope. i will put the write up as i go. these are much more powerfull for the price. i got a 5000btu A/C unit for less than $80US dollars. that is nearly a 1/2 hp chiller!. 6000 is a 1/2 hp. small fridges like that are only 1/10hp to 1/6 hp. not a lot of power there. the rest of the idea is the same put the coils in a cold bath and run a legnth of tube through it. the longer the better.

G~

[Phishnoob]

That is a great idea Geoff. Before we had AC we had one of those hang in the window things that really chilled the entire place.

Let us know how the project progresses. Also, I am really interested in how you will run the interface from the tank to the cooling piping. I would worry a little bit about blocking the flow out of the unit and overheating it, but if you stick a tub right in front that goes halfway up then you might be on to something.

We have every other type of pointy head on this forum...maybe there is an AC and R guy lurking.

I will check the ratings on the motor and compressor tonight, but I would imagine the AC unit is an order of magnitude better than my beer fridge. The only drawback is that you have to go all the way to the kitchen if you get thirsty working on your tank.

Phishnoob

[Geoff]

here is a thread with Mafia and Greg talking about theirs.

i plan on just twisting the cooling array down into a vertical possition and submerging it into the bath. copper is very maliable, slowly.

G~

[pomme]

yeah have decided i will get a chiller, to do the job. will be expensive but for my piece of mind and the love of my corals i think it will be worth it.

[Phishnoob]

I was thinking of using a brake tubing bender to make big oval shaped coils. My only worry would be gunk collecting in the turns but if the radiuses were gentle hopefully it would work.

Is stainless steel a no no in the tank?

Phishnoob

[Geoff]

only the highest grade stainless would work. i can not remember the #'s right now. the others will rust over time. these high grade stainless approach the price of titanium, so this is why you see all of the chillers use titanium.

G~

[Kevin1000]

It is darn tough to put together a DIY chiller and I think there are few people who can put together an effective one. Much better off buying a used chiller than trying to cluge together one that won't work.

Heres a link on putting together a chiller

http://www-2.cs.cmu.edu/~cap/raid/chillers/diy/

For anyone following this thread thinking about using a small fridge as a chiller - don't. Simply will not work.

http://www-2.cs.cmu.edu/~cap/raid/ch...dge/index.html

[Phishnoob]

Mine works..two degrees. It is probably not really efficient but 80 is in the green on my thermometer and 82 was in the yellow. I will do a temperature study this weekend after ditching the plastic for a titanium coil. The factors considered in doing mine were the flow rate (slow slow slow), the contact area of the tubing to the water bath which the coil will improve, and the heat transfer coefficient of the tubing. Plastic tubing as Geoff mentioned is a great insulator so I would imagine that titanium will be much better. I have six loops of 1/2" tubing in the water bath currently tie wrapped to form a coil.

I know a used chiller is a good bargain but all of the tubing and fittings for my project cost $11.77 including the PVC cement.

I read the analysis of the beer fridge chiller and I agree with all of his points except that he seems to refer to air to water heat transfer. The only way this works is to keep a large water bath around the coils. Pumping this through cold air would be about as useless as...oops nm.

Of course we have 10 percent humidity, good A/C and a perfect climate here so the effectiveness of the chiller is the best it gets. Also, there is only a total volume in the tank and sump of 105g or so and the big tank guys would need more to help.

You guys in the south buy a chiller (and bugspray /snickers)

Phishnoob

[Geoff]

Phish-do you check your PM's? i sent you one a while ago about Ti tubing.

G~

[Phishnoob]

Hi Geoff,

I check my PM's a lot but for a while did not know that deleted ones still took up space until you really got rid of them.

Is a titanium coil okay? I know that metal is not easy to work with at all and if copper is okay that would be way better.

Phishnoob

[Geoff]

titanium is the way to go. copper is prolly the worst you could use.

what size Ti do you have access to? even a short length of Ti will do wonders to the efficiency of the chiller. the biggest problem with using Ti or any metal will be the interface between the plumbing and the chiller. most Ti does not come threaded.

G~

[Phishnoob]

At www.mcmastercarr.com they have 1,3 and 5 foot pieces of both titanium and monel. There is also inconel.

I used to work as a nuclear engineer on submarines and those were the metals of choice for use near salt water. They have special annealed welded and drawn titanium that is supposed to be malleable. A five foot piece is pretty expensive at 100 bucks but I think a three foot section is perfect for my beer fridge (dorm fridge for you teetotalers) and it can be worked. They sell the compression fittings as well so let me figure out how to do this.

I will post pics and test data in a week or so unless for some reason they have a titanium coil at Lowes for a bump start.

This will be a good chance to match up my beer fridge chiller against Geoff's room AC chiller if we can get good data and costs. This is not a contest at all, but there is so much to say good and bad about each DIY project and it sort of comes down to a cost vs. benefit thing. Both versions seem like they will work as long as the tubing is some sort of corrosion resistant metal in a water bath, but the room AC has way better ratings for cooling and if the cooling can be transferred to the flow will work better. Also, even if my fridge is a POS it does not matter...made it myself

Phishnoob

[Geoff]

don't i wish HD or Lowe's would carry Ti!

my chillers gonna kick your chillers butt.

actually we will have a third type of DIY chiller in the mix. my old one was a DIY made from an old water fountain. this worked pretty will. always kept my 200g total system within .5 degree of set temp. that was a 1/5 HP chiller. it finally ran out of freon. i have no idea how old it was, but i am thinking close to 15-20yrs. so it was no surprise.

so far i have a 6000 btu A/C unit, a large cooler, 100' of 1/2" tubing, and a automotive creeper.

i have started taking pics, so hopefully i can get a nice write up later this weekend.

BTW-i guess macmastercar is down. i will try later.

i can get all of the inconel i want. as long as it was in welding wire form. my dad works for a company that does repairs on nuclear reactors and other kinds of power plants.

G~